One of the brain's remarkable capabilities is the ability to integrate information from very different sources to produce a coherent picture of the external world. This enhances its ability to detect, localize and identify environmental events. There is now a good deal known about how this "multisensory integration" is effected in individual neurons in the superior colliculus (SC), a midbrain structure involved in orientation behavior. SC neurons react to combinations of cross-modal cues by significantly enhancing their responses, a physiological enhancement in stimulus salience. This, in turn, leads to an enhancement of orientation to the initiating event. Unfortunately, the computational operations that have evolved to produce these enhanced responses and the behaviors that depend on them, remain unknown. Nevertheless, there is an implicit assumption that the underlying processes are unique to multisensory integration and differ from the processes that have evolved to integrate within-modal information. Though reasonable, there is little data to support this contention. It appears equally, if not more, reasonable to postulate that SC neurons have evolved similar integrative computational processes to effect similar behaviors regardless of the specificity of their inputs. Common computational mechanisms would avoid complicating even further the brain's formidable task of binding information from different sources. The objective of this proposal is to determine what these multisensory computational processes are, whether they differ from those used in unisensory integration, whether they are dependent on higher-order (cortical) influences and how they relate to the production and control of attentive and orientation responses to external events. They should also be helpful in the clinic by providing us with insights that can enhance the use of multisensory strategies in rehabilitating patients with sensory neglect syndromes due to traumatic brain injury or developmental disorders of sensory systems.